In communications networks having a plurality of network nodes, the processes performed by the network nodes may be adapted to one another. For this purpose, methods for time synchronization in which clocks contained in the network nodes are synchronized to the clock of a master node are used. One example of a method for time synchronization is the Precision Time Protocol, which is defined in the IEEE 1588 and IEEE 1588v2 standard, respectively. In this protocol, a synchronization message is sent out with the timestamp of the clock of the master mode to other network nodes in the form of slave nodes. The slave nodes update the time information contained in the synchronization message based on delays estimated by the slave nodes, which take into consideration the transmission time of the synchronization message from the preceding network node and an internal processing time.
Conventional methods for time synchronization have the disadvantage that, in the case of a fault in the master node, the synchronization becomes faulty in all slave nodes, which leads to a fault propagation with regard to the timing characteristic in the entire communications network. As a consequence, synchronism may no longer be guaranteed for all parts of the network.